This invention relates to a dielectric liquid impregnant for electrical devices and more particularly to an electrical capacitor utilizing an improved dielectric liquid impregnant.
Liquid impregnants for electrical capacitors should have a high dielectric constant, maintain a low dissipation factor, and be compatible with other materials utilized in the capacitor structure. At the same time, the impregnant must withstand elevated and fluctuating temperature, pressure, and voltage stress conditions with excellent electrical characteristics for a long operative life of the capacitor.
The polychloroinated biphenyls as capacitor impregnants meet these requirements and they were eminently satisfactory for several decades. The polychlorinated biphenyls are broadly referred to as PCBs. The polychlorinated biphenyls have recently been associated with ecological problems, restrictive use limitations, and rising costs. These problems have spurred the search for a suitable replacement capacitor impregnant which would have some advantageous impregnant characteristics comparable to those of the chlorinated biphenyls, and still provide outstanding electrical and compatibility performance with the two most important present day capacitor solid dielectrics, paper and polypropylene. Isopropyl biphenyl (IPB) has been suggested as providing good electrical characteristics as a dielectric fluid impregnant.